A known fuel injection valve, which injects fuel to supply the fuel in an internal combustion engine, includes a nozzle for injecting the fuel and an actuator for driving the nozzle in a valve opening direction and a valve closing direction. The nozzle of the fuel injection valve includes a nozzle body, which is shaped into a cylindrical tubular form, and a needle, which is received in an inside of the nozzle body in such a manner that the needle is movable in an axial direction of the nozzle body. Injection of fuel from the nozzle body is started or stopped by moving the needle in the axial direction in the inside of the nozzle body.
Specifically, a seat portion is formed in an inner wall of the nozzle body, and a seatable portion of the needle, which is formed at a location adjacent to a tip end of the needle in the axial direction, is seatable against the seat portion. Furthermore, a plurality of injection holes extends through a portion of the inner wall, which is located on the tip end side of the seat portion. When the seatable portion of the needle is lifted from the seat portion, the fuel is guided from the inside of the nozzle body to the outside of the nozzle body and is injected (see, for example, JP2010-180763A).
Various studies have been conducted to increase a flow coefficient, which indicates a degree of flowability of the fuel, in order to implement an advantageous structure, which is advantageous in terms of the energy, in the fuel injection nozzle.
For example, in the nozzle of JP2010-222977A, an opening of the injection hole at the inside of the nozzle body is shaped into a semi-ellipse form, so that generation of cavitation in the injection hole or localization of the flow of the fuel can be limited, and thereby the flow coefficient can be improved.
Furthermore, in the nozzle of JP2014-208991A, a longitudinal length of an inlet of the injection hole, which is measured in a direction perpendicular to a circumferential direction of the nozzle body, is set to be larger than a longitudinal length of an outlet of the injection hole, which is measured in the direction perpendicular to the circumferential direction of the nozzle body. In this way, an upstream end of the inlet can be placed at a further upstream side, so that a turn angle of the fuel flow can be reduced to increase the flow coefficient.
However, the flow coefficient of the fuel injection nozzle is reduced when the injection pressure of the fuel is increased. Thus, the increase of the injection pressure is disadvantageous in terms of the energy. Therefore, it has been demanded to improve the flow coefficient in applications where the high injection pressure of the fuel is demanded like in a case of a fuel injection valve that directly injects the fuel into a cylinder of, for example, a diesel engine.